#!/usr/bin/env node

const { Readable  } = require('stream');

let c = 'a'.charCodeAt(0);

class MyReadable extends Readable {
  constructor() {
        super();
          
  }

  _read() {
        this.push(String.fromCharCode(c++));
        if (c>'z'.charCodeAt(0)) {
                this.push(null);
                    
        }
          
  }

}

let rs = new MyReadable();
rs.pipe(process.stdout);
